Browsing by Subject "urban green spaces"
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(2023)Climate change severely threatens ecosystem services and human well-being: vegetation and soils underneath it can be particularly vulnerable to climate warming. Soils hold the largest carbon stock in terrestrial ecosystems, and urban park soils, especially in cool climates, can hold remarkable carbon stocks and may be able to offset some atmospheric CO2 emissions. Land use changes, such as urbanization, influence soil organic carbon formation and soil carbon storages. In this study, I was interested whether three vegetation types (deciduous trees, conifers and lawn) differ in their capacity to store C in their rhizosphere, and whether this is affected by park size. I measured the proportion of tree canopy layer in class A park areas of the city of Helsinki, to estimate soil C storages of these areas and to examine C density (kg C m-2). Proportions of tree canopy layers in different park size groups were measured using QGIS and ortographs. Soil C storages were calculated using existing soil C data and average proportions of conifer and deciduous trees in parks of the city of Helsinki. Park size had a significant effect on proportion of the tree canopy coverage: canopy cover decreases with an increase in park size. Especially large parks are dominated by lawn. The average soil C densities in small, medium and large parks were 23.98 kg C m-2, 23.47 kg C m-2 and 23.15 kg C m-2, respectively. However, the overall proportion of conifer canopy in parks of the city of Helsinki is rather small, resulting in small differences in C densities between different park size categories, despite significant differences in tree canopy coverage between the three size groups. Most of the stored soil C in parks of the city of Helsinki are under lawn, even though it is the least efficient of the three studied vegetation types (deciduous trees, conifers, lawn) in soil C sequestration. Within a park size category and at park level, large parks store the highest amount of carbon per park. Even so, at the city level, the total amount of carbon is highest in the small parks due to their high number. Conifer trees associate with improved C sequestration to soils compared to deciduous trees and lawn. Increasing the amount of conifer trees in urban parks thus likely increase the important C storages of these soils. Results of this study highlight the importance of the contribution of urban parks and especially conifer trees in carbon sequestration. Future research related to urban soil C sequestration and the effects of vegetation type and climatic conditions is needed to better understand soil C accumulation and how the C sequestration of urban park soils could be enhanced.
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(2023)Tiivistelmä - Referat - Abstract To aim for a just and sustainable society, it is essential to consider how we manage cities and to reflect on the role of young people as agents for successful future generations. The school system must take on the responsibility of developing a sense of social justice amongst young people. However, few learning activities are established to promote learning about environmental and intergenerational justice issues, and are usually limited to a top-down approach based on STEM disciplines (Science, Technology, Engineering and Mathematics). In this work, I argue that education in sustainability needs to be opened to a relational approach that introduces new justice perspectives, becoming a driver for active citizenship and public participation. The thesis is based on ten workshops conducted in Kumpula, Helsinki, involving 197 students from two upper secondary schools. The novelty of this work consists in addressing a specific range of upper secondary school students (16 to 19) and combining cognitive and relational learning activities to elicit reflections on environmental justice. I used a learning activity based on a Role-play method to actively involve students in working with justice perceptions and nature-based solutions. The analysis is based on a mixed methods- approach where the statistical analysis (pretest-posttest) and qualitative content analysis support each other. The innovative integration of cognitive and relational learning contributed to a deeper knowledge of urban green space management. This approach elicited new recognition justice perspectives by enhancing the participants’ awareness of community values and needs, comprehending both humans and non-humans. After the learning activity, students were generally more willing to make their voice heard by policy makers and to participate in public discussions. Based on the findings, more resources and time would be needed to build a long-term project in order to assess the permanence of relational and cognitive learning and more widely the efficacy of this approach for transformative learning.
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